The biological, chemical, and physical characteristics and the serological role of the major glycoprotein at the surface of the TA3-Ha cell are investigated and compared to the properties of the strain specific, TA3-St, subline. Studies of the chemical structure of the carbohydrate moiety include the distribution of the chains on the polypeptide core by electron microscopy with the use specific lectins. The biosynthesis and the factors affecting the physicochemical characteristics of the glycoprotein at the surface of TA3-Ha cells in suspension culture will also be investigated. Attempts to determine the structure of the carcinoembryonic antigen will use inhibition by synthetic glycopeptides.